Chris joined Award Solutions in 2000, bringing his expertise in GSM and IS-136 technologies and wireless network planning. He specializes in telecommunications systems, focusing in GSM, GPRS, and UMTS systems, wireless and Internet applications, and the convergence of communication technologies. Currently, he is working on LTE, UMTS, IP Multimedia Subsystem, IP telephony, HSPA+, and Wireless Network Planning. He has over 19 years of experience in the wireless telecom industry.
Chris began his career in the wireless telecommunication industry. He spent the first nine years in the Wireless Systems Engineering department at Nortel Networks. As a Member of Scientific Staff, Chris worked on network planning, customer support, bid support, and capacity planning for low power wireless systems and Personal Communications Systems. He moved into the GSM and IS-136 field as a manager. These responsibilities included working with customers to plan, expand, and manage their existing wireless network. This position evolved into managing the GSM, IS-136 and IS-95 core network capacity team as a Senior Manager. In the role of Senior Manager, Chris worked with the development teams, product test teams, marketing teams, and product line management teams in the determination and requirement establishment of the subscriber capacity of these systems. This included presenting capacity information directly to customers and influencing them in their network evolution direction.
Currently, Chris is a Principal Consultant at Award Solutions. His current focus is LTE, 4G, OFDMA, UMTS/HSPA+, IP convergence, and Network Planning. His interests include the planning of the LTE radio network and core network; service planning in the LTE core network and mobile devices; and interoperations and mobility between LTE and the 3G networks. He is also responsible for helping in the mentoring of new instructors in UMTS and LTE.
Chris holds a Master's degree in Computer Science Telecommunications from the University of Missouri at Kansas City as well as Bachelor's degree in Computer Science and Mathematics from Cameron University. Chris also holds 4 patents in the area of wireless technology.
LTE has been designed to support packet services in a more efficient manor than UMTS. The key service, from a wireless data network perspective, is the establishment of the data session that will be used by the mobile device for data services. In UMTS and GPRS, the key to establishing a data session is the Packet Data Protocol (PDP) Context establishment procedure. In LTE, the procedure has been changed to an Evolved Packet System (EPS) Bearer Setup. Let’s take a look at the differences.
In a UMTS network the data session is established with a PDP Context Activation procedure. But, before the PDP context can be established the UE must do an Attach procedure. The Attach procedure is used to alert the SGSN (Serving GPRS Support Node) that the UE has powered up. The problem is that there isn’t anything the UE can do after an Attach without requesting a PDP Context. To be fair, after an Attach the UE is available to receive a SMS or a Network Initiated PDP Context. The problem is that we don’t do SMS over the packet network and we don’t do Network Initiated PDP Context in practice.
After the Attach procedure is completed the UE will then do a Primary PDP Context that will establish the data session and allocate an IP address to the UE. This PDP Context will have a QoS associated with it based on the needs in the request. If the UE needs to have multiple data sessions, due to various Quality of Service (QoS), the UE will do a Secondary PDP Context activation. For the sake of completeness, it is important to note that there are other reasons to establishing subsequent PDP Context beyond QoS, but that is a good place to start.
In a LTE based system, there are two types of data session setups. The first is called a Default EPS Bearer. The second is the Dedicated EPS Bearer. The first is established as part of the Attach procedure. The Default EPS Bearer will only support a nominal QoS, but that should be sufficient for application signaling. When the UE needs to establish a service a Dedicated EPS Bearer will be established. This will have the QoS requirements needed for the service.
As way of comparison, the LTE Attach/Default EPS Bearer will be equivalent to the UMTS Attach and then doing a Primary PDP Context establishment procedure. The Secondary PDP Context Activation is similar to the Dedicated EPS Bearer Setup procedure. So, there is a variation of a theme here, but not a significant difference.
If we were to look at the key parameters in these messages, we would see that both the UMTS procedures and the LTE procedures still use parameters like an Access Point Name (APN), IP address type, and QoS parameters. Therefore, the only real difference between the two types of procedures is that there has been an optimization in LTE that reduces the number of signaling messages that need to be sent over the air.
If suppose LTE device attached to LTE network and so default bearer is activated. Later, user activated one more bearer(not dedicated) but with a different APN, now can we deactivate the original default bearer and just retain the new one ? So what happens if we do detach now ? will the new one get deactivated ?
It's true LTE doens't have complicated NBAP protocol :-)